ComboFix is an excellent but powerful tool.
Running ComboFix by yourself is like performing open heart surgery on yourself--the scalpel and other surgical tools that is ComboFix is meant to be wielded by a highly trained surgeon
only in emergencies or dire circumstances. When the surgeon is thru s/he leaves the room. So ComboFix should be removed from a system once it has accomplished its job, unlike an AV that is there to protect you from future infections.
No one should be using ComboFix unless
specifically instructed to do so by a Malware Removal Expert who can interpret the logs. It is a powerful tool intended by its creator to be "
used under the guidance and supervision of an expert",
NOT for general public or personal use. ComboFix was never meant to be used as a general purpose malware scanner like SuperAntispyware or Malwarebytes' Anti-Malware which scan individual drives or different folders on a computer for viruses.
Using this tool incorrectly could lead to disastrous problems with your operating system such as preventing it from ever starting again.